用光辐照法在SBN:Cr晶体中写入动态阵列平面光波导

Fabrication of dynamic planar waveguide array in SBN:Cr crystals by structure-light irradiation

利用扩展的准直He_Ne激光束通过菲涅耳双棱镜所形成的干涉光场辐照SBN :Cr晶体 ,同时沿晶体光轴方向施加适当的直流电场 ,可在晶体中形成类似于体相位光栅结构的阵列平面光波导 .采用马赫_曾德干涉仪光路实时测量了所写入阵列平面光波导的横向折射率分布 ,其峰值接近 1 0 - 4.初步的导光测试结果表明 ,利用周期结构光辐照并辅以适当的外加电场在SBN :Cr晶体中写入阵列平面光波导是可行的 .并且由于SBN :Cr晶体的快速响应特性 ,所写入的光波导是动态的 ,可随着写入光的撤除而快速消失 ,或通过改变双光束夹角而写入不同周期的阵列平面光波导 ,从而实现阵列光波导的动态控制 .此外 ,通过改变外电场的大小可以有效地控制写入波导区折射率的大小 。

A planar waveguide array, whose structure is similar to a volume phase grating,can be fabricated in a congruent SBN:Cr (Sr 0 61 Ba 0 39 Nb 2O 6:Cr) crystal by irradiation of two_beam interference pattern,and,simultaneously, by applying an appropriate direct electrical field along the c _axis of the crystal. The transversal index profile of the waveguide array is measured in real time using a Mach_Zehnder interferometer,and the maximum index change in the waveguide region is close to 10 -4 . The initial guiding tests show that it is feasible to write a dynamic planar waveguide array in the SBN:Cr crystal by using irradiation of period structure_light,due to the rapid response property of SBN:Cr crystals. And the dynamic control of the waveguide can be realized by switching the writing lights on or off,or adjusting the angle of the two interferent beams. Moreover,the waveguide parameter such as the index profile in the waveguide zone can be effectively controlled by varying the external electric field.